Madrid have secured the once-capped Brazil player on a six-year contract, with the club reported to have triggered his €50million release clause.
Ajax ended their dominance in Europe too, with a stunning 5-3 aggregate win in the Champions League last-16.
Real Madrid management informed Zidane about this signing on his arrival and the French coach has agreed to it.
Militao: new Real Madrid signing
Zidane said: "Isco just wants to play football, nothing else".
"We want to think positively and defeat Celta tomorrow, I do not want to think about anything else, but the players are keen to show what they are worth".
Real president Florentino Perez has again turned to Zidane, who stepped in for Rafa Benitez in 2016.
Bale started only three of Solari's last 11 games in charge, but Zidane said: "I am not going to speak about Bale's season". What I can tell you is that these two players have a lot of quality.
Zidane has been heavily linked with another of his old sides, Juventus, in recent weeks. This is the first stone of the new project, but Los Blancos would need to sign many more players in the transfer window. Flying Betis left-back Junior Firpo is under consideration with Marcelo still likely to leave but Madrid could recall Achram Hakifi a year early from his loan spell at Dortmund.